Setting a radio communication base station apparatus in the inside of a building such as an ordinary home or an office has been discussed, the radio communication base station apparatus covering a small cell (femtocell) having a cell radius of several tens of meters or less (referred to as “femtocell base station” or “Home Node-B (HNB)” or the like).
The femtocell base station under consideration in 3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) is also considered to allow only limited group members to have access. For example, when set at a home, the femtocell base station limits access only to family members of the home. Such a cell may be referred to as CSG (Closed Service Group) cell.
In this case, a UE (User Equipment) that is a mobile terminal granted access to the cell is preferentially connected to the femtocell base station. That is, when entering the area of the femtocell base station, the UE is preferentially connected to the femtocell base station, even if the UE can receive radio waves of an existing base station covering a cell having a larger cell radius than a femtocell (hereinafter, referred to as “macrocell” or “macrocell base station”).
In general, a macro base station is interfered with radio waves transmitted by other macro base stations, and thus the macro base station is set in consideration of, for example, the distances to adjacent macro base stations so as not to generate interference. However, an operation is studied in which a user can voluntarily change the place to set the femtocell base station; hence, the femtocell base station placed in a cell of the existing macrocell will interfere with the macro base station at high probability. In addition, the number of femtocell base stations may become an order of tens of thousands or hundreds of thousands in some cases, which will significantly influence the existing macrocell base station. As a means of avoiding such interference, there is a method to receive averaged frequency resource information of the macro base station, to set a resource allocation recurrence threshold, and to preferentially allocate a frequency resource in the femtocell to a resource lower than the threshold.
In order to solve a case that the interference narrows the area of the femtocell base station, the femtocell base station applies a function for detecting the radio waves condition around the femtocell base station and adjusting output so as to minimize influence on the existing macrocell base station.
Patent literature 1 discloses a mobile communication system for acquiring information about the use of radio resources by the neighboring base station apparatus, through a mobile station apparatus present close to the neighboring base station apparatuses. The mobile communication system disclosed in patent literature 1 is configured, based on the acquired information, to prohibit a target base station apparatus from using a radio resource being used by the neighboring base station apparatus or to make it difficult to allocate user data to the radio resource.